Optical systems such as lens modules, still cameras, video cameras, telescopes and other portable imaging devices are prone to have a movement during imaging process. The movement of the optical systems can come from many sources including hand shaking (e.g. in still or video cameras), environmental vibration (e.g. in moving vehicles), and/or earth's rotation (e.g. in astronomical applications). These movements can cause a critical problem especially in long exposure time (low light condition) or with long focal length setting (telephoto) by resulting in severely blurred images.
Various approaches for image stabilization have been developed in order to compensate the movement of the optical system occurring during the imaging process. These include mechanical image stabilization, optical image stabilization, and digital image stabilization. In the mechanical image stabilization, the image sensor is moved with respect to the camera body to counteract the movement of the optical system. On the other hand, in the optical image stabilization, the optical path of light is changed by using movable lenses, floating lenses, or variable angular prisms to compensate the movement of the optical system. The movement of the optical system can be detected by conventional angular velocity detection sensors such as vibration gyros, MEMS (Micro-Electro Mechanical System) sensors, and piezoelectric sensors.
FIGS. 1 and 2 show conventional optical image stabilization devices. FIGS. 1a-1c are schematic diagrams showing a conventional optical image stabilizing device using a movable lens. In FIGS. 1a-1c, the optical system 11 (e.g. still cameras, video cameras, or other type of imaging devices) includes an optical image stabilization device. The optical image stabilization device 11 comprises a lens 12 configured to change the optical path 13 of light to an image sensor 14. FIG. 1a shows the optical system 11 having no movement during the imaging process. The optical system 11 with no movement produces a clear image A. FIG. 1b shows the optical system 11 having movement during the imaging process but without movement compensation. Since there is no movement compensation, the optical system 11 produces a blurred image on the image sensor 14 since the image traverses across the image sensor (from A to B) FIG. 1c shows the optical system 11 with movement, wherein the movement compensation is in operation. To compensate the movement of the optical system 11, the optical image stabilization device measures the movement of the optical system 11 using one or two angular velocity sensors and controls the lens 12 to have a proper movement (e.g. up, down, left, or right) to adjust the optical paths 13 of light in accordance with measured movement information. By adjusting the optical paths 13 of light, the image C remains clear on the image sensor 14 during the imaging process. In the conventional optical image stabilization devices, the lens 13 is moved macroscopically by coil motors or electromagnetic attraction.
FIGS. 2a-2c are schematic diagrams showing another type of conventional optical image stabilizing device using a variable angle prism. The optical system 21 includes an optical image stabilization device. The optical image stabilization device comprises a variable angle prism 22 configured to change the optical paths 23 of light to an image sensor 24. FIG. 2a shows the optical system 21 with no movement during the imaging process. The optical system 21 with no movement produces a clear image A. FIG. 2b shows the optical system 21 with the movement during the imaging process but without movement compensation. Since there is no movement compensation, the optical system 21 produces a blurred image on the image sensor 24 since the image traverses across the image sensor (from A to B). FIG. 1c shows the optical system 21 with movement during the imaging process, wherein the movement compensation is in operation. To compensate the movement of the optical system 21, the optical image stabilization device measures the movement of the optical system 21 using one or two angular velocity sensors and controls the variable angle prism 23 to have a proper shape change to adjust the optical paths 23 of light in accordance with measured movement information. By adjusting the optical paths 23 of light, the image C remains clear on the image sensor 24 during the imaging process.
These conventional image stabilizing devices involve with macroscopic movement or macroscopic shape change of lenses, prisms, or image sensors. The macroscopic movement or macroscopic shape change of the optical elements can cause the optical system to have slow response time, increased volume and weight, complex structure and operation, and eventually low image quality. The present invention resolves these problems of conventional optical image stabilizing devices by using the MEMS technology. The MEMS optical image stabilizing device of the present invention provides fast speed, light weight, simple operation, and high image quality image stabilization for the optical system.